I'm not sad to see him go and if I'm honest I'm generally happy with the release clause.
I imagine the clause was instrumental in his initial signing for us and we did get some good service out of him to begin with. As many have alluded to he is clearly a talented footballer; if he had continued to show this and with better management the clause would have been irrelevant. Should we have sold him earlier when we had better offers? In hindsight yes (financially) but it would have been a clear signal that we had given up at Christmas cashing in on an asset because we were concerned his value would drop if relegated.
My one problem, and I think this says more about modern footballers, how genuine were his attempts to keep us up knowing that he was guaranteed a payday if we went down? For me, it is almost as bad as those players who, after relegation, bleed their clubs dry taking wages that they know the club can not afford.
Good luck to Leicester, you may have a bargain, you may have a wrong un.